Modern portable audio systems such as smartphones, tablet computers, and smart speakers, present unique challenges when seeking to increase their audio output power. There are of course restrictions in the available physical volume inside their housings, which means that the audio subsystem components have to not only be small but also cope with limited heat dissipation capability. A further difficulty in producing a sufficiently loud and high quality sound, and especially music playback, is how to do so without rapidly depleting a limited power source, namely a rechargeable battery.